Light sources having high luminance can be realized with the combination of a pump radiation source having a high power density, such as a laser, and a phosphor element that is arranged at a distance therefrom and emits conversion light upon excitation with the pump radiation. During operation in transmission, the pump radiation is here incident on a pump radiation input coupling surface, and the conversion light is output at a conversion light output coupling surface of the phosphor element, which is opposite with respect to the former, and used for illumination purposes. It is here not necessary for the entire pump radiation to be converted (complete conversion), but a non-converted part thereof can also be used, downstream of the phosphor element, together with the conversion light in a mixture (partial conversion).
The conversion light is typically emitted in Lambertian fashion at the conversion light output coupling surface. Even if the pump radiation upstream of the phosphor element is generally focused, i.e. a corresponding beam has an opening angle of only a few degrees, in the case of the partial conversion, the non-converted part of the pump radiation is then fanned out downstream of the phosphor element in a manner that is comparable to the conversion light, for example owing to scatter processes in the phosphor element.